1. Field of the Invention
The present invention relates to an organic light emitting device and a method of manufacturing the same, and more particularly, to an organic light emitting device including an emissive layer, of which an no−ne parameter is greater than an no−ne parameter of a single-coated emissive layer where no is an ordinary refractive index and ne is a extraordinary refractive index and a method of manufacturing the same.
2. Description of the Related Art
Organic light emitting devices (OLEDs) are self-emissive devices that emit light by combination of electron and holes in a fluorescent or phosphorescent organic layer when an electric field is supplied to the organic layer. OLEDs are lightweight, have simple structures, produce high-quality color images with wide viewing angles, and can be easily manufactured. In addition, OLEDs can produce moving images with high color purity at a low operating voltage and using low power consumption. Due to these characteristics, OLEDs are suitable for portable electronic devices.
OLEDs are divided into small molecular OLEDs (SMOLEDs) and polymer OLEDs (PLEDs) according to the molecular weight of an emissive layer forming material.
In SMOLEDs, an organic layer including at least an emissive layer may have a multi-layer structure by further including a hole injection layer, a hole transport layer, an electron transport layer, and/or an electron injection layer to allow holes and electrons to efficiently flow. These layers can be manufactured by vacuum thermal deposition, organic vapor jet deposition, organic vapor phase deposition or the like. In this case, however, materials for forming these layers are inefficiently used, and thus, the manufacturing costs increase. In addition, proper deposition equipments for producing large screens have not been developed.
On the other hand, an organic layer interposed between first and second electrodes of a PLED has higher mechanical strength and better thermal stability than that of a SMLED. In addition, PLEDs operate at low voltage and can emit various emission colors according to the structure of an emission polymer. The organic layer of the PLEDs can be formed by spin casting, ink jet printing, nozzle printing or spray printing an emissive polymer dissolved in an organic solvent. Therefore, research on PLEDs and methods of manufacturing the same are actively conducted.
U.S. Pat. No. 5,247,190 discloses a light emitting device comprising a poly(p-phenylenevinylene) (PPV)-based polymer film. In this case, a phenylene ring of the PPV-based film contains at least one substituent selected from an alkyl group (preferably, methyl group), an alkoxy group (preferably, methoxy group or an ethoxy group), halogen (preferably, Cl or Br), and a nitro group. In this patent, the PPV-based polymer film was formed by repeating a unit process, the unit process including: spin coating an ionic group-containing PPV precursor dissolved in an organic solvent, such as methanol, on a predetermined substrate: and heat treating the result to form an insoluble thin film. As a result, a multilayer including the insoluble thin film is formed.
A method of forming layers by spin self-assembly was disclosed at Cho et al. Adv. Mater. (2001), 13, p 1076. However, this method can be applied only to a polymer containing an ionic group, and the thickness of a single-coated layer obtained from the method is in the range of as little as 1 nm to 2 nm. Accordingly, when an organic layer of a PLED is formed using this method, a manufacturing time is long and manufacturing costs are high.
As described above, when an organic layer, in particular, an emissive layer interposed between first and second electrodes is formed using conventional methods, characteristics of the organic layer do not meet a required standard.